JPH01115193A - Flexible printed wiring board - Google Patents

Abstract

PURPOSE:To improve heat resistance and folding resistance by forming a flexible epoxy resin support of flexible epoxy resin composition containing as a curing agent polythiol compound. CONSTITUTION:A flexible epoxy resin support is formed of flexible epoxy resin composition containing as a curing agent polythiol compound. The polythiol as the agent most preferably includes pentaerythritol tetrakis. The composition is formed, in addition to polythiol compound, epoxy resin main agent and amine curing catalyst. The polythiol compound particularly contributes to the flexibility of the film. Thus, folding resistance and heat resistance are improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a flexible printed wiring board, and the flexible printed wiring board of the present invention can be used in electronic equipment, communication equipment, home appliances,
It can be used as printed wiring boards for office automation equipment, automobiles, cameras, toys, etc.

[Conventional technology]

The materials used as the base film for metal foil-coated resin films used in the manufacture of flexible printed circuit boards are mostly polyimide films and polyester films, with glass-epoxy-based films also being used. Slightly used.

Polyimide film has excellent heat resistance that withstands soldering, making it the most versatile base material for flexible printed circuit boards and used in many applications, but it is hygroscopic and prone to cracking. It has the disadvantage of being easy. Furthermore, the very high price is an obstacle and limits the field of application.

Although polyester film has problems in terms of heat resistance and flame retardancy, it is inexpensive and is a material that is very well balanced in other properties. Therefore, it does not require soldering and is used in large quantities in fields where flame retardancy is not required.

Glass-epoxy based films have good heat resistance and
Although it has low hygroscopicity, it has a drawback of poor folding durability, so its field of use is limited.

[Problem to be Solved by the Invention 9] As mentioned above, among the materials used as base films for flexible printed wiring boards, polyimide films are expensive, highly hygroscopic, and tear easily, while polyester films have poor heat resistance. However, glass-epoxy resin films have disadvantages such as poor durability and flame retardancy, and glass-epoxy resin films have poor folding durability.

Therefore, an object of the present invention is to provide a flexible printed wiring board that has excellent folding durability by taking advantage of the characteristics of an epoxy resin that has excellent heat resistance and low hygroscopicity.

[Means for solving problems]

The above object is to provide a flexible printed wiring board comprising a conductive wiring pattern and a flexible epoxy resin support according to the present invention, wherein the flexible epoxy resin support is a flexible printed wiring board containing a polythiol compound as a hardening agent. This can be achieved by the above-mentioned flexible printed wiring board, which is characterized in that it is formed from a flexible epoxy resin composition.

The flexible printed wiring board may include heat-resistant fiber cloth as a reinforcing material. As the polythiol compound as a curing agent for the flexible epoxy resin composition, pentaerythritol tetrakis (mercaptopropionate) is most preferred.

The flexible epoxy resin composition used in the present invention serves as a base film for a flexible printed wiring board, and is intended to impart flexibility, heat resistance, low moisture absorption, and other basic properties to the film. used in The composition consists of an epoxy resin base, a polythiol compound curing agent, and an amine curing catalyst. Polythiol compounds in particular contribute to the flexibility of the film.

Furthermore, in order to impart flame retardancy to the film, a brominated epoxy resin base material may be used, and various organic flame retardants and inorganic flame retardants may also be added.

As the epoxy resin base resin, known, especially commercially available, various grades of epoxy resins can be used. for example,
Bisphenol A-based epoxy resin main agent, for example, formula (1-
1) A compound represented by the formula (%) (where n is 0 or a positive integer), a bisphenol F-based epoxy resin main agent, for example, the formula (
1-2) A compound represented by the formula (1-3) as a novolac type epoxy resin base compound (where n is O or an integer of 2 or less, and R
is a hydrogen atom or CH, a group),
Brominated epoxy resin base agents, such as compounds represented by formula (1-4) (where n is an integer of 1 or more, and m is 0 or a positive integer), cycloaliphatic epoxy resin base agents, glycidyl ester type Resins such as compounds represented by the formula (1-5) % formula %), diglycidyl p-oxybenzoic acid,
Dimer acid diglycidyl ester, glycidylamine-based epoxy resin base agents, such as compounds represented by formula (1-6), formula (1-7), and formula (1-8), hydantoin-type epoxy resin base agents, such as 2(1-9) ) (Here, RII is -GHz- or -GHz-CI-
0-CHz-H3), triglycidyl isocyanurate,
Polypropylene glycol diglycidyl ether For example, compounds represented by the formula (1-10) (% formula %) (where n is a positive integer), bisphenol S diglycidyl ether, resorcinol diglycidyl ether, hexahydrobisphenol A diglycidyl Examples include ether, neopentyl glycol diglycidyl ether, and brominated novolak type epoxy resin base. In addition to being used alone, these epoxy resin base resins can be used in combinations of two types depending on the purpose.
More than one type can be used in combination. From the viewpoint of availability, price, and properties of the epoxy resin obtained after curing, bisphenol A type epoxy resin (formula (11
)), bisphenol F-based epoxy resin [formula (1-2)
), novolac type epoxy resin [formula (1-3>3, brominated epoxy resin C formula (1-4)), polypropylene glycol diglycidyl ether [formula (1-10)) and brominated novolac type epoxy resin are preferred .

The polythiol compound used in the present invention has 2 or more SH groups, preferably 2 to 4, particularly 3 to 4 SH groups.
Aliphatic and cycloaliphatic compounds.

Preferred polythiol compounds are straight-chain polythiol compounds having 2 or more 5Hi, preferably 2 to 4, with an intervening oxygen or sulfur atom, a hydroxy group or lower alkyl group as a substituent, and 6 or more carbon atoms; It is a branched or cyclic aliphatic hydrocarbon compound. Preferred polythiol compounds include, for example, polyether polythiols such as polyhydroxyethylene polythiol or polyhydroxypropylene polythiol, cyclic ether polythiols such as trioxymethylene trithiol, and the like. As a polyether polythiol compound, for example, formula (2-1)% formula%) (where n is 0 or a positive integer, particularly 1-5,
m is an integer greater than or equal to 2, particularly 2 to 4, and R+ is m
or a compound represented by the formula (2-2) (where n is a positive integer, especially 4 to 10) can be used.

Furthermore, preferred polythiol compounds include mercaptocarboxylic acids, especially mercapto-saturated aliphatic monocarboxylic acids of 2 to 6 carbon atoms (e.g. mercaptoacetic acid, mercaptopro-and-ionic acid, mercaptobutanoic acid, mercaptopencunic acid, or mercaptocarboxylic acids). Esters of polyhydric alcohols (hexanoic acid) and polyhydric alcohols, especially dihydric to tetrahydric alcohols (eg glycols, glycerin, trimethylolpropane, pentaerythritol or 1,2,3-trihydroxycyclohexane) can be used.

As this ester, for example, formula (2-3) [where R2 is a hydrogen atom or -CH, group, and R3 is -(
Hz) #- group, β is an integer from 1 to 5, and n
is O or a positive integer, especially from 0 to 5, m is an integer of 2 or more, especially from 2 to 4, and R4 is an m-valent aliphatic group, such as a saturated aliphatic group having m to m+3 carbon atoms or is an alicyclic hydrocarbon residue] It is preferable to use a compound represented by the following.

The above polythiol compounds can be used alone or in combination of two or more. Since polythiol compounds generally have a bad odor, it is practically preferable to use a polyhydric alcohol ester of mercaptocarboxylic acid, which has less odor. For example, the compounds listed below are preferred. Namely, Glycerin Tris (Mercaptoacetate), Glycerin Tris (Mercaptopropionate), Glycerin Tris (Mercaptobutyrate), Glycerin Tris (Mercaptopentanoate)
, Trimethylolpropane Tris (Mercaptoacetate), Trimethylolpropane Tris (Mercaptopropionate), Trimethylolpropane Tris (Mercaptobutyrate), Trimethylolpropane Tris (Mercaptopentanoate), Trimethylolpropane Tris (Mercaptohexanoate) ate), pentaerythritol tetrakis (mercaptoacetate), pentaerythritol tetrakis (mercaptopropionate),
Pentaerythritol tetrakis (mercaptobutyrate), pentaerythritol tetrakis (mercaptopentanoate), pentaerythritol tetrakis (mercaptohexanoate), glycerin tris (polypropylene glycol mercaptopropionate) or 1,2,3-trihydroxycyclohexane tris (Polypropylene glycol mercaptopropionate).

Among the polythiol compound curing agents, pentaerythritol tetrakis (mercaptopropionate) is most preferred from the viewpoints of viscosity, odor, curing performance, price, and the like.

As the amine curing catalyst, polyamines, tertiary amine compounds, and imidazole compounds, which are generally used as curing agents for epoxy resins, can be used alone or in combination of two or more. Examples of polyamines include aliphatic polyamines, polyamide polyamines, alicyclic polyamines, aromatic polyamines, dicyandiamide, and adipic dihydrazide. Examples of the tertiary amine compound include aliphatic tertiary amines, alicyclic tertiary amines, heterocyclic tertiary amines, and aromatic tertiary amines. The imidazole compounds are represented by the general formula (3-1) group, -C+dhs group, or side) group, R5 is a hydrogen atom or a -C113 group, and Rc is a hydrogen atom, -CI+2- Examples include compounds represented by G> group and -C[h-CHz-CN group. General formula (3-1
), the substituents R,,R, and R
Many types with different e are used.

Antioxidants, moisture resistance improvers, adhesion agents, fillers, coupling agents, and solvents (reactive and non-reactive) may be added to the flexible epoxy resin composition as required for each purpose and use. , colorants, dispersants, antisettling agents, thickeners, and other various additives may be optionally blended. The blending ratio of the components of these compositions can be arbitrarily selected depending on the purpose, use, etc. Typically, 10 parts by weight of the polythiol compound curing agent is added to 100 parts by weight of the epoxy resin base resin.
~150 parts by weight (preferably 20 to 100 parts by weight) and 0.01 to 20 parts by weight (preferably 0.01 to 20 parts by weight) of an amine curing catalyst.
05 to 15 parts by weight) is used.

The heat-resistant fiber cloth optionally used in the present invention is a woven or non-woven fabric made from glass fibers, aromatic polyamide fibers, carbon fibers, ceramic fibers or asbestos fibers, and has a thickness of 30 to 200 m (preferably 30 m). 1 to 5 sheets (preferably 1 to 3 sheets) of cloth impregnated with a flexible epoxy resin composition are used.

The flexible printed wiring board according to the present invention can be manufactured by any conventionally known method.

For example, first a metal foil-coated epoxy resin film consisting of a conductive metal foil and a flexible epoxy resin support is manufactured,
Subsequently, a flexible printed wiring board is manufactured from the metal foil-covered epoxy resin film.

The conductive metal foil used to produce the metal foil coated epoxy resin film described above can be formed from any metal that can exist in foil form. Typical metals used in the production of the above-mentioned films are, for example, copper, silver, aluminum, nickel, tin and zinc, which are good conductive metals. As the copper foil, electrolytic copper foil and rolled copper foil can be used.

The thickness of the metal foil is not particularly limited, but is generally 5-100 μm, preferably 15-70 μm.

The flexible epoxy resin (uncured) composition is applied to the metal foil. As a coating method, for example, a knife coater, a spray coater, a roll coater, a blade coater, and a spin coating can be used. For example, when using a knife coater, a flexible epoxy resin (uncured) composition liquid is applied to the metal foil running on a backup roll to a uniform thickness with a knife, and then heated in a heating furnace. It can be manufactured by a hardening and winding method, and a film with a thickness of 50 m to 250 m is formed, and the thickness including the metal foil is 55 m to 350 m!
A metal foil-coated epoxy resin film of m is obtained. In addition, a metal foil-coated epoxy resin film containing heat-resistant fiber cloth as a component is produced by heat-pressing a heat-resistant fiber cloth impregnated with a flexible epoxy resin (uncured) composition liquid onto a metal foil, and then heating it in a heating oven. A fiber reinforced film with a thickness of 80 to 300 mm is formed, and the thickness including the metal foil is 85 to 400 mm.
A metal foil-coated epoxy resin film of fo) is obtained.

Subsequently, from the metal foil coated epoxy resin film,
The flexible printed wiring board of the present invention can be manufactured by any conventionally known method.

For example, a copper foil coated epoxy resin film wound into a roll may be rolled to roll.

It can be manufactured by processing in the following order: surface cleaning, drying, screen printing, drying, etching, water washing, drying, coverlay film lamination, punching, and cutting using the roll method.

Furthermore, instead of the step of laminating the coverlay film, it can also be manufactured by performing solder resist printing.

〔Effect of the invention〕

Whereas conventionally used glass cloth-epoxy resin film-based boards have poor folding durability and have limited application, the flexible printed circuit board of the present invention has excellent folding durability and heat resistance. It has excellent properties, and is also cheaper than the polyimide film-based 5a tentative.
Because it has excellent moisture absorption, which is a disadvantage of polyimide film, it is not only possible to expand the field of use of flexible printed wiring boards, but also has poor heat resistance compared to polyester film, which is another conventional base film. It can also be used in fields where it could not be used.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.
It goes without saying that the technical scope of the present invention is not limited by these Examples.

In addition, the blending amounts in the following examples are parts by weight.

Epicoat 828 (oiled shell epoxy
61 parts of pentaerythritol tetrakis (mercaptopropionate) (hereinafter abbreviated as PTMP) as a curing agent and 6.8 parts of metaxylylene diamine (hereinafter abbreviated as MXDA) as a curing catalyst were defoamed and mixed. Using a knife coater, the uncured epoxy resin composition was rolled into 18 m+ thick copper foil [Fukuda Metal Foil & Powder Kogyo ■]
It was applied uniformly onto the surface of the product and cured by heating at 120° C. for 60 minutes. The obtained copper foil-coated epoxy resin film with a thickness of 150 mm was tested according to the bending strength test (JIS l"8115
In the MIT method test (R=1.5), it showed a bending strength of 700 times. In comparison, a comparative copper foil-coated epoxy resin film made using triethylenetetramine as a curing agent only exhibited a 200 fold strength.

When a flexible printed wiring board was manufactured from the copper foil-coated epoxy resin film of this example by a roll-to-roll manufacturing method, the dimensional accuracy of the wiring pattern was good, and the heat resistance due to the molten solder plating process was good. No dimensional changes were observed. In addition, cracks were less likely to occur during the punching process for external shaping, and the product was less likely to tear during the subsequent assembly process, resulting in a high yield of products.

Scrap ±1 80 parts of Epicoat 828 as the epoxy resin main ingredient and novolac type epoxy resin Araldite ECN-1235
A copper foil-coated epoxy resin film with a thickness of 180 mm was prepared in the same manner as in Example 1, except that 20 parts of 20 parts of 20% of the epoxy resin film (manufactured by Nippon Ciba Geigy) was used. Showed strength.

A flexible printed wiring board was produced from the obtained copper foil-coated epoxy resin film in the same manner as in Example 1.
The dimensional accuracy of the wiring pattern and the dimensional stability against heat were good, and cracks were less likely to occur during the punching process, and the product yield was high even in the subsequent assembly process.

Implementation ±1 A copper foil-coated epoxy resin film with a thickness of 120 cm was prepared in the same manner as in Example 1, except that 100 parts of Araldite This film showed a folding strength of 800 times.Furthermore, a flexible printed wiring board was produced from this film in the same manner as in Example 1. It had good physical properties.

60 parts of Epicoat 5050 (manufactured by Yuka Shell Epoxy ■), which is a brominated epoxy resin as the main epoxy resin, and 32 parts of Araldite CY221 (manufactured by Nippon Ciba Geigy ■), which is a polypropylene glycol diglycidyl ether-based epoxy resin. A mixture of 8 parts of a bromine-containing reactive diluent shell block [manufactured by Yuka Shell Epoxy ■] was used, and 36 parts of PTMP as a curing agent and 3.0 parts of 2-methylimidazole as a curing catalyst were defoamed and mixed. Using the uncured epoxy resin composition, a copper foil-coated epoxy resin film having a thickness of 200 units was produced in the same manner as in Example 1. This film showed a durability of 900 folds.

The copper foil was removed from this film by etching and [IL94
When the flammability was measured, it showed vo flame retardancy.

The obtained copper foil-coated epoxy resin film was cut into a sheet shape to produce a flexible printed wiring board. Each process (
The processability in screen printing, etching, coverlay film lamination, punching, and cutting was good, and a flexible printed wiring board with a wiring pattern with good dimensional accuracy was obtained. The adaptability to post-processing (metting, external hole processing, reinforcing plate processing, etc.) was also excellent, and a good wiring board was obtained.

(n=approximately O-3) and (n=approximately O-3) polythiol compound A
A W4 foil-coated epoxy resin film with a thickness of 150 μm was prepared in the same manner as in Example 1, except that 80 parts of TO-317M (manufactured by Asahi Denka ■) was used.
It shows the folding strength of 3 times.

When a flexible printed wiring board was produced from the obtained film in the same manner as in Example 4, it showed the same good properties as in Example 4.

6 to 12 and to 1 to 4 Bisphenol A-based epoxy resin Epicoat 828 and polypropylene glycol diglycidyl ether-based epoxy resin Araldite CY-2 as epoxy resin main ingredients
21 with a different blending ratio and PTM as a curing agent.
Example 6 shows the composition of the epoxy resin composition and film properties of a copper foil-coated epoxy resin film produced using a roll coater using P and 2-ethyl-4-methylimidazole (hereinafter abbreviated as EMIM) as a curing catalyst. ~
Table 1 shows a case where amines were used as a curing agent as Comparative Example No. 12.

According to Table 1, it can be seen that the copper foil-coated epoxy resin film used in the present invention has excellent properties and can be used as a substrate for flexible printed wiring boards.

The tA foil-covered epoxy resin films obtained in Examples 6 to 12 were each cut into sheets, and flexible printed wiring boards were produced in the same process. All films had good processability, produced wiring patterns with excellent dimensional accuracy, and were products with excellent adaptability to post-processing.

1501 in the same manner as in Example 1, except that 70 parts of CupCure 3-800 (manufactured by Yuka Shell Epoxy ■), which is a polyether polythiol represented by formula (2-1), was used as the actual flLL chemotactic hardening agent. A thick copper foil coated epoxy resin film was prepared. This film exhibited a strength of 600 folds.

A flexible printed wiring board was produced from this film in the same manner as in Example 1, and similarly good products were obtained.

H5-(CzH40CHzOCJt-SS +-b C
zll*0CH20CJt-3H [Thiocol LP-3
A copper foil-coated epoxy resin film having a thickness of 150 mm was prepared in the same manner as in Example 1, except that 100 parts of the film was used. This film exhibited a strength of 600 folds.

A flexible printed wiring board was produced from this film in the same manner as in Example 1, and similarly good products were obtained.

Shikami Mondo i A mixture of 60 parts of Epicoat 828 and 40 parts of Araldite CY-221 as an epoxy resin base, 59 parts of PTMP as a curing agent, and EMIM as a curing catalyst.
0.1 part was defoamed and mixed.

The uncured epoxy resin composition was impregnated into a plain-woven glass cloth (manufactured by Unitika ■, basis weight: 26 g/m) with a thickness of 35 mm, and three sheets of the impregnated glass cloth were stacked on top of a rolled copper foil with a thickness of 18 parts m. After being pressure-bonded, it was heated and cured in an oven at 120°C for 60 minutes. The resulting copper foil-coated epoxy resin film had a thickness of 210 degrees and a folding strength of 500 times. In addition, the tensile strength is 1,500 kg/cd,
The value was considerably higher than the 250 kg/cd without glass cloth.

An epoxy resin film containing glass cloth as a constituent material has lower folding strength than an epoxy resin film not containing glass cloth, but has improved mechanical strength and excellent processing characteristics.

A flexible printed wiring board was produced from the obtained film in the same manner as in Example 4, and a similarly good product was obtained.

Claims (1)

[Claims] 1. In a flexible printed wiring board comprising a conductor wiring pattern and a flexible epoxy resin support, the flexible epoxy resin support is formed from a flexible epoxy resin composition containing a polythiol compound as a curing agent. The flexible printed wiring board as described above.